The primary goal of the Collaborative Study on the Genetics of Alcoholism (COGA) is the elucidation of the genes responsible for susceptibility to alcohol dependence. The COGA project, initiated in 1987, is a large scale family study of alcoholism being conducted at six sites nationwide. The initial clinical assessment has been completed on over 1800 probands and their biological relatives (total N=12,800) and a five-year follow-up is underway.